There are systems, such as, for example, synchronous motors and generators, which supply electrical current to a rotor winding by way of slip rings. The current is typically applied to the slip rings via brushes mounted on a fixed conducting ring. Ordinarily the slip rings are at low voltage, however, the slip rings may be used in high voltage applications.
A slip ring assembly for use in high voltage machines and applications is disclosed in U.S. Pat. No. 6,465,926 issued Oct. 15, 2002 to Rehder et al entitled Cleaning/Cooling of High Power Rotary Current Collection System. This patent discloses an electrical current collector system that includes for each phase a fixed conducting ring; brushes; an electrically conductive slip ring; and a slip ring support assembly. Cooling air is circulated through the collector system for high voltage rotating machines and is exhausted from collector housing through a cylindrically shaped exhaust passageway and filtering device. This passageway also includes the bus bar that feeds power to and from the fixed conducting ring. Typically, the cooling air stream passes over the brushes in the collector system and in so doing the cooling air moves and carries carbon particles or dust produced as a result of brush wear out through the exhaust duct passageway in the bus bar. This passageway, however, is limited in cross-sectional area due to the primary purpose of the bus bar to carry current. Hence the air flow is limited. Any build up of carbon particles can result in shorting of the windings of the machine if not properly removed from the air flow.
Accordingly, there is a need in high voltage collector systems for rotating machines and transformers to have an exhaust passageway that provides an insulated exhaust passageway between the high voltage environment of the collector system and the ground potential beyond the exhaust passageway that allows collector cooling air to pass through the exhaust passageway unimpeded and without the exhaust passageway being prone to creep buildup of carbon particles along its inner surfaces. Further, there is a need to filter the collector cooling air after it passes through the exhaust passageway.